Potential Azure Browser SSO Abuse

Status: test
Severity: low
Log source: product windows, category image_load
Author: Den Iuzvyk
Source: github.com/SigmaHQ/sigma

Detects abusing Azure Browser SSO by requesting OAuth 2.0 refresh tokens for an Azure-AD-authenticated Windows user (i.e. the machine is joined to Azure AD and a user logs in with their Azure AD account) wanting to perform SSO authentication in the browser. An attacker can use this to authenticate to Azure AD in a browser as that user.

MITRE ATT&CK coverage

Tactic	Techniques
Execution	`T1574.001` Hijack Execution Flow: DLL
Stealth	`T1574.001` Hijack Execution Flow: DLL

Event coverage

Provider	Event	Title
Sysmon	Event ID 7	Image loaded

Rule body yaml

title: Potential Azure Browser SSO Abuse
id: 50f852e6-af22-4c78-9ede-42ef36aa3453
status: test
description: |
    Detects abusing Azure Browser SSO by requesting OAuth 2.0 refresh tokens for an Azure-AD-authenticated Windows user (i.e. the machine is joined to Azure AD and a user logs in with their Azure AD account) wanting to perform SSO authentication in the browser.
    An attacker can use this to authenticate to Azure AD in a browser as that user.
references:
    - https://posts.specterops.io/requesting-azure-ad-request-tokens-on-azure-ad-joined-machines-for-browser-sso-2b0409caad30
author: Den Iuzvyk
date: 2020-07-15
modified: 2023-04-18
tags:
    - attack.persistence
    - attack.privilege-escalation
    - attack.execution
    - attack.stealth
    - attack.t1574.001
logsource:
    category: image_load
    product: windows
detection:
    selection:
        ImageLoaded: 'C:\Windows\System32\MicrosoftAccountTokenProvider.dll'
    filter_main_bgtaskhost:
        Image|startswith:
            - 'C:\Windows\System32\'
            - 'C:\Windows\SysWOW64\'
        Image|endswith: '\BackgroundTaskHost.exe'
        # CommandLine|contains: '-ServerNameBackgroundTaskHost.WebAccountProvider'
    filter_optional_devenv:
        Image|startswith:
            - 'C:\Program Files\Microsoft Visual Studio\'
            - 'C:\Program Files (x86)\Microsoft Visual Studio\'
        Image|endswith: '\IDE\devenv.exe'
    filter_optional_ie:
        Image:
            - 'C:\Program Files (x86)\Internet Explorer\iexplore.exe'
            - 'C:\Program Files\Internet Explorer\iexplore.exe'
    filter_optional_edge_1:
        - Image|startswith: 'C:\Program Files (x86)\Microsoft\EdgeWebView\Application\'
        - Image|endswith: '\WindowsApps\MicrosoftEdge.exe'
        - Image:
              - 'C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe'
              - 'C:\Program Files\Microsoft\Edge\Application\msedge.exe'
    filter_optional_edge_2:
        Image|startswith:
            - 'C:\Program Files (x86)\Microsoft\EdgeCore\'
            - 'C:\Program Files\Microsoft\EdgeCore\'
        Image|endswith:
            - '\msedge.exe'
            - '\msedgewebview2.exe'
    filter_optional_onedrive:
        Image|endswith: '\AppData\Local\Microsoft\OneDrive\OneDrive.exe'
    filter_optional_null:
        Image: null
    condition: selection and not 1 of filter_main_* and not 1 of filter_optional_*
falsepositives:
    - False positives are expected since this rules is only looking for the DLL load event. This rule is better used in correlation with related activity
level: low

Stages and Predicates

Stage 0: `condition`

selection and not 1 of filter_main_* and not 1 of filter_optional_*

Stage 1: `selection`

selection:
    ImageLoaded: 'C:\Windows\System32\MicrosoftAccountTokenProvider.dll'

Stage 2: `not filter_main_bgtaskhost`

filter_main_bgtaskhost:
    Image|startswith:
        - 'C:\Windows\System32\'
        - 'C:\Windows\SysWOW64\'
    Image|endswith: '\BackgroundTaskHost.exe'

Stage 3: `not filter_optional_*`

filter_optional_devenv:
    Image|startswith:
        - 'C:\Program Files\Microsoft Visual Studio\'
        - 'C:\Program Files (x86)\Microsoft Visual Studio\'
    Image|endswith: '\IDE\devenv.exe'
filter_optional_ie:
    Image:
        - 'C:\Program Files (x86)\Internet Explorer\iexplore.exe'
        - 'C:\Program Files\Internet Explorer\iexplore.exe'
filter_optional_edge_1:
    - Image|startswith: 'C:\Program Files (x86)\Microsoft\EdgeWebView\Application\'
    - Image|endswith: '\WindowsApps\MicrosoftEdge.exe'
    - Image:
          - 'C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe'
          - 'C:\Program Files\Microsoft\Edge\Application\msedge.exe'
filter_optional_edge_2:
    Image|startswith:
        - 'C:\Program Files (x86)\Microsoft\EdgeCore\'
        - 'C:\Program Files\Microsoft\EdgeCore\'
    Image|endswith:
        - '\msedge.exe'
        - '\msedgewebview2.exe'
filter_optional_onedrive:
    Image|endswith: '\AppData\Local\Microsoft\OneDrive\OneDrive.exe'
filter_optional_null:
    Image: null

Exclusions

Top-level NOT(...) conjuncts: predicates this rule actively suppresses.

Field	Kind	Excluded values
`Image`	starts_with	`C:\Windows\SysWOW64\`
`Image`	starts_with	`C:\Windows\System32\`
`Image`	ends_with	`\BackgroundTaskHost.exe`
`Image`	ends_with	`\msedge.exe`
`Image`	ends_with	`\msedgewebview2.exe`
`Image`	starts_with	`C:\Program Files (x86)\Microsoft\EdgeCore\`
`Image`	starts_with	`C:\Program Files\Microsoft\EdgeCore\`
`Image`	starts_with	`C:\Program Files (x86)\Microsoft Visual Studio\`
`Image`	starts_with	`C:\Program Files\Microsoft Visual Studio\`
`Image`	ends_with	`\IDE\devenv.exe`
`Image`	ends_with	`\AppData\Local\Microsoft\OneDrive\OneDrive.exe`
`Image`	ends_with	`\WindowsApps\MicrosoftEdge.exe`
`Image`	eq	`C:\Program Files (x86)\Internet Explorer\iexplore.exe`
`Image`	eq	`C:\Program Files (x86)\Microsoft\Edge\Application\msedge.exe`
`Image`	eq	`C:\Program Files\Internet Explorer\iexplore.exe`
`Image`	eq	`C:\Program Files\Microsoft\Edge\Application\msedge.exe`
`Image`	is_null	(no value, null check)
`Image`	starts_with	`C:\Program Files (x86)\Microsoft\EdgeWebView\Application\`

Indicators

Each row is a field, operator, and value that the rule matches. The corpus column counts how many other rules in the catalog look for the same combination: high numbers point to widely-used, community-vetted indicators. Blank or 1 shows that the indicator is specific to this rule.

Field	Kind	Values
`ImageLoaded`	eq	`C:\Windows\System32\MicrosoftAccountTokenProvider.dll`

`j` / `k`	Scroll down / up
`d` / `u`	Half-page down / up
`gg` / `G`	Top / bottom
`h` / `l`	History back / forward
`f`	Follow link (`Shift` = new tab)
`/`	Focus search
`?`	Toggle this help
`↑` / `↓`	Navigate search results
`Enter`	Open highlighted result
`Esc`	Close results / dialog

`type:`	`events` / `rules` / `providers`
`vendor:`	`sigma` / `elastic` / `splunk` / `kusto` / `chronicle` (vendor name alone also works: `sigma:`, `kql:`, `secops:`…)
`tactic:`	TA-id, slug, or name: `credential_access`, `TA0006`
`technique:`	technique or sub-technique ID: `T1003`, `T1003.001` (alias `tech:`)
`severity:`	`critical` / `high` / `medium` / `low` / `informational` (alias `sev:`)
`risk_score`	Numeric comparison on the Elastic risk score (0 to 100): `risk_score>50`, `risk_score<=20`, `risk_score=99` (alias `risk`; Elastic rules only)
`stages:`	Rules with exactly N pipeline stages
`correlation:`	`single_event` / `sequence` / `alternatives` / `alternatives_cross_log` / `all_required` / `correlated`
`with:`	Co-occurrence event-id; stacks (`with:4624 with:4769`) to require all, while a comma list in one occurrence (`with:4624,4769`) is an either-or group. Implies multi-event
`like:`	Structural neighbors of a rule slug (equivalents + subsumption stricter / broader): `like:comsvcs_lsass_memory_dump-splunk-sysmon`
`groupby:`	Entity-grouping substring match against `group_by_keys`: `groupby:user`, `groupby:host`
`uses:`	Rules whose predicate tree touches the field (any kind, any value): `uses:CommandLine`
`excludes:`	Rules with top-level `not()` clauses on the field (FP whitelists): `excludes:ParentImage`
`field:` / `value:`	Predicate search; narrows rule cards to those with a matching leaf and drives the indicator tier. Unquoted = substring, wildcards allowed (`value:mimikatz`)
`indicator:`	Shorthand for `field:F value:V`: `indicator:Image=*\powershell.exe`
`kind:`	Filter by predicate kind. Narrows rule cards to those carrying a matching predicate leaf (`vendor:elastic kind:cidr_match`) and drives the indicator tier: `contains` / `starts_with` / `ends_with` / `regex` / `cidr` / `eq` / `in` … (operator aliases `op:`/`match:`)
`has:` / `no:`	`sample`, `field`, `notes`, `refs`, `trace`, `thirdparty`, `rule`, `pattern`, `timewindow`, `threshold`, `newterms`, `sigma`/`elastic`/`splunk`/`kusto`/`chronicle`
`-op:val`	Exclude matches; works on most operators but not `type:`/`like:`/`has:`/`no:` (use `no:<flag>` to exclude a rule flag): `tactic:execution -vendor:splunk`. Standalone `-kind:`/`-field:`/`-value:` drop every rule carrying a matching predicate leaf (`type:rules -kind:is_null`)
`field:"…"` / `value:"…"`	Quoted value = anchored exact match (also allows spaces): `value:"net user"`
`a,b`	Comma = OR inside one operator (`vendor:sigma,elastic`, `severity:high,critical`); repeating a facet merges the same way. `field:`/`value:` never split (literal commas)
`vendors:` / `stage:`	Singular and plural spellings fold to the canonical operator and value: `tactics:` = `tactic:`, `type:event` = `type:events`, `correlation:sequences` = `correlation:sequence`, `has:thresholds` = `has:threshold`
`"quoted phrase"`	Exact-match a multi-word phrase (free text)

Potential Azure Browser SSO Abuse

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_main_bgtaskhost`

Stage 3: `not filter_optional_*`

Exclusions

Indicators

Keyboard shortcuts

Search operators

Potential Azure Browser SSO Abuse

MITRE ATT&CK coverage

Event coverage

Rule body yaml

Stages and Predicates

Stage 0: condition

Stage 1: selection

Stage 2: not filter_main_bgtaskhost

Stage 3: not filter_optional_*

Exclusions

Indicators

Stage 0: `condition`

Stage 1: `selection`

Stage 2: `not filter_main_bgtaskhost`

Stage 3: `not filter_optional_*`